1. Technical Field of the Invention
The present invention relates to an image forming device for scan exposing a recording material in the sheet form with laser light and the like, and developing the recording material while conveying it.
2. Description of the Related Art
In recent years, in the medical field, an image forming device by a dry system which is free from use of solution based treating chemicals and does not require wet processing is watched from the viewpoints of environmental conservation and space saving. In this image forming device, for films of a photosensitive and heat-sensitive recording material or a heat development photosensitive material (hereinafter simply referred to as “recording material”), laser light is irradiated (scanned) in an exposure section to form a latent image; the recording material is heat developed upon contact with heating means in a heat development section; and after cooling, the recording material having an image formed therein is discharged from the device.
In this kind of image forming device, in irradiating the recording material with laser light to record image information therein, it is required to smoothly convey the recording material so as to give neither vibration nor impact, thereby ensuring a precise irradiation action of the laser light. According to such a demand, for example, in a light beam scanning device disclosed in JP-B-5-45109, there is described a construction in which a nip roller 5 is provided in the tip of an arm 3 swingablly centering around a swinging axis 1 as illustrated in FIG. 10. A transmission roller 7 is rotatably supported at the other end of the arm 3, and the transmission roller 7 and the nip roller 5 are tightly stretched by a belt 9 as rotation transmission means. The nip roller 5 is rotated via the belt 9 by rotation drive of a drive roller 11 slidably contacting with the transmission roller 7. A cam plate 15 in the disc form is connected via a swinging rod 13 in the arm 3 in the side of the nip roller 5, and the arm 3 is capable of swinging via the swinging rod 13 by the rotation of the cam plate 15.
In this construction, when a recording material 19 guided by a guide plate 17 reaches the drive roller 11, the drive roller 11 is rotated, and following this rotation, the nip roller 5 is rotated. At the same time, as illustrate in FIG. 10B, when the cam plate 15 is rotated in the counterclockwise direction, the swinging rod 13 rotates the arm 3 in the counterclockwise direction, and the nip roller 5 presses the tip portion of the recording material 19. As a result, when the recording material 19 is sandwiched between the nip roller and the drive roller 11, the recording material 19 does not receive an impact at all and is conveyed as it is. Accordingly, during this period, even when laser light is scanned to record image information on the recording material, no disturbance of the recorded image is generated.
However, when such a swinging mechanism by a nip roller is employed, since exclusive drive mechanism and drive source are required, not only the structure became complicated, but also the number of parts increased, resulting an increase of the production costs.
On the other hand, there is proposed a plate sub-scanning mode capable of surely conveying a recording material in the sheet form by a simple structure. In this plate sub-scanning mode, in a sub-scanning conveyance section 21 as illustrated in FIG. 11, two drive rollers 23, 25 are provided while sandwiching the major scanning line of laser light, and a guide plate 27 for supporting the recording material 19 is provided opposing to these drive rollers 23, 25. The guide plate 27 is provided with slope portions 29, 31 for warping the recording material 19 to be inserted between the guide plate 27 and the respective drive rollers 23, 25 along a part of each peripheral face of the drive rollers; and a press portion 33 composed of substantially horizontal planes for receiving an elastic repulsive force caused by the warp of the recording material 19 between the drive rollers upon contact therewith.
In this construction, when the recording material 19 enters from the tip of the slope portion 29, the tip of the recording material 19 comes into a space between the guide plate 27 and the drive roller 23. At this time, since the press portion 33 and the slope portion 29 of the guide plate 27 are bent at a prescribed angle φ, when the recording material 19 moves into the press portion 33 from the slope portion 29, it warps, and an elastic repulsive force is generated in the recording material itself by this warp. By this elastic repulsive force, a prescribed friction force is generated between the recording material 19 and the drive roller 23, and a conveyance drive force is surely transmitted into the recording material 19 from the drive roller 23, thereby smoothly conveying the recording material 19.
Also, the recording material to be used in this type of image forming device has a plural number of sizes such as B4 (257×364 mm), HANSETSU (14×17 inch), and MUTSUGIRI (8×10 inch). For this reason, in the conventional image forming devices, magazine trays for accommodating a recording material are provided for every size, and all of these trays are detachably installed in the multi-stage state in the lower portion of the device, etc., thereby making it possible to cope with a variety of sizes.
However, in the foregoing image forming device of a plate sub-scanning mode, though it is possible to smoothly convey the recording material 19 by a simple structure without giving a vibration or an impact as compared with the nip roller mode as illustrated in FIG. 10, the guide plate 29 composed of the slope portions 29, 31 and the press portion 33 is required to have an extremely high dimensional accuracy, an aspect of which became a factor to increase the production costs of device.
Also, for the purpose of enabling the image forming device to cope with a variety of sizes of recording materials, it generally accommodates a plural number of trays accommodating recording materials of a different size in the multi-stage state. For this reason, the size of the device becomes large, an aspect of which was contradictory to the demand for compactness. Also, the recording material of the uppermost layer of each tray is allowed to stand in the exposed state within the device. In the case of a recording material having high sensitivity to the humidity, and in the case of a user who does not consume a large amount of the recording material, there was the possibility that the exposed recording material is dried out to cause a fluctuation of the density (scattering such that the density is not precisely expressed). On the other hand, there are proposed a shutter mechanism in which a discharge port of the tray is opened only at the time of discharging the recording material; and a mechanism in which at the time of discharging the recording material, an open and close seal is wound and a discharge port is opened, and after discharging, the discharge port is again sealed by means of adhesion of the open and close seal. However, all of these mechanisms are complicated, an aspect of which was contradictory to the demand for compactness, resulting an increase of the costs of the device.
On the other hand, in order to enhance the sealing properties, there is proposed a heat development device using a rolled recording material as illustrated in FIG. 12 and disclosed in JP-A-9-274300. This heat development device makes it possible to use both a cut recording material and a rolled recording material. That is, whether the recording material is a cut recording material 35 or a rolled recording material 37 is detected by a form judgment unit 39. The form judgment unit 39 is provided with a sensor 41 provided in an introduction passage of the cut recording material 35 and a sensor 43 provided in an introduction passage of the rolled recording material 37. In this heat development device, the rolled recording material 37 in which a latent image has been previously formed by laser light is accommodated in a magazine 45. The rolled recording material 37 sent out from the magazine 45 is conveyed into a heating furnace 47, held by a heater drum 51 to be rotation driven by a motor 49, and then heat developed by heating of a halogen heater 53. That is, this heat development device does not convey an unexposed recording material.
Accordingly, though feed of the rolled recording material is carried out, this heat development device does not aim to ensure the sealing properties of an unexposed recording material but aims to make it possible to use both the cut recording material and the rolled recording material. For this reason, this heat development device is provided with a mechanism for feeding both the cut recording material and the rolled recording material and is contradictory to the demand for the compactness. Also, though this heat development device has a construction of use of the rolled recording material, it is not provided with a countermeasure to a recording material that when allowed to stand in the exposed state, may possibly cause a density fluctuation.
Under these circumstances, the invention has been made.